Concept and numerical analysis of a double-stage coupling damper for multilevel seismic protection

A new double-stage coupling damper (DSCD), consisting of a friction component (FC) and a buckling restrained component (BRC) in series, is proposed for improving the seismic performance of structures under multilevel earthquakes. A robust numerical model for the DSCD is established based on experimental testing of conventional dampers. This numerical model explores the effects on the performance of the double-stage hysteresis behaviour of the ratio between the friction force of the FC and the yield force of the BRC, Rfy, as well as the length of slotted holes in the inner plate, Lsh and the number of FCs, Pfc. The results show that the energy dissipation capacity and the double-stage energy dissipation characteristics of the DSCD decrease with increasing Rfy and Lsh. The energy dissipation capacity of the DSCD with the single-sided FC is also higher than that of the two-sided FCs. Furthermore, a simple finite element model of the double-stage damper for general application in structural analysis is developed and validated against the detailed model. The simplified model is defined in OpenSees and applied to the nonlinear seismic analysis of single-degree-of-freedom structures. The results show that the DSCD reduces the displacements and accelerations of the structure more than the conventional BRB in most cases and for various seismic intensity levels.